The present invention relates to a serial data communication apparatus for a time sharing computer system or the like having a plurality of transceivers.
In such a system, a main or key station such as a central processing unit of a computer communicates with a plurality of local stations or units for data communication. The procedure is for the main station or unit to first transmit an address code indicating the local unit which is to receive the transmission and then transmit the desired data. Only the local station corresponding to the address code is energized to receive the transmission.
Whether transmission is on a character by character basis or a block by block basis, some means must be provided to discriminate the address codes from data.
Conventionally, the address codes are preceded by a special address identification code which indicates that the following group of signal bits constitutes an address code. A start code is generated preceding each character or block of data and an end code is generated following the data.
The conventional systems are unnecessarily low in transmission speed due to the fact that so many identifier codes must be transmitted along with the actual data.